Current-speed relationship for instantaneous suction detection algorithm in lvads

ABSTRACT

A system for detecting a suction condition in an implantable blood pump including a controller in communication with the blood pump. The controller includes a control circuit configured to calculate a present value during a time period, the present value corresponding to a pump speed divided by a pump current, determine a plurality of data values during the time period based on the present value, and determine a suction detection threshold value using the plurality of data values. The control circuit is also configured to compare the present value during the time period to the suction detection threshold value and generate an alert when the present value exceeds the suction detection threshold value on a plurality of instances during the time period, the alert corresponding to a suction condition.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Application Ser. No.62/672668, filed May 17, 2018.

FIELD

The present technology is generally related to a system and method fordetecting an adverse event, such as a suction condition, within animplantable blood pump.

BACKGROUND

Implantable blood pumps are commonly used to assist the pumping actionof a failing heart. Typically, blood pumps include a housing with aninlet, an outlet, and a rotor mounted therein. The inlet may beconnected to a chamber of the patient's heart, typically the leftventricle, using an inflow cannula. The outlet may be connected to anartery, such as the aorta. Rotation of the rotor drives blood from theinlet towards the outlet and thus assists blood flow from the chamber ofthe heart into the artery. A blood pump may be configured as aventricular assist device (“VAD”). Exemplary VADs include the HVAD® pumpand the MVAD® pump manufactured by HeartWare, Inc. in Miami Lakes, Fla.,USA. The HVAD® pump is further discussed in U.S. Pat. No. 8,512,013 andthe MVAD® pump is further discussed in U.S. Pat. Nos. 8,007,254 and9,561,313, the disclosures of which are incorporated herein in theentirety.

To provide clinically useful assistance to the heart, VADs impel bloodat a relatively substantial rate. However, when the VAD is operated at aflow rate in excess of the inflow rate of blood to the ventricle, theVAD will create a suction condition within the ventricle and theventricle may collapse from the blood deficiency. A suction conditionmay also be produced when the intake or outlet of the VAD is obstructed.The suction condition causes a decline in flow rate which creates avacuum, thereby causing the pump speed to significantly increaserelative to a normal operative speed. In response thereto, the currentmay be reduced in an effort to return the pump speed to the normaloperative speed. Unfortunately, known systems and methods may detect thesuction condition using a flow waveform, which delays the time ofdetection, thereby increasing the risk of harm to the patient.

SUMMARY

The techniques of this disclosure generally relate to a system andmethod for detecting an adverse event, such as a suction condition,within an implantable blood pump.

In one aspect, the present disclosure provides a system for detecting asuction condition in an implantable blood pump including a controller incommunication with the blood pump, the controller including a controlcircuit configured to: calculate a plurality of data values using ahysteresis window, calculate a present value during a time period, thepresent value corresponding to a pump speed divided by a pump currentfollowing the hysteresis window, determine a suction detection thresholdvalue using the plurality of data values, compare the present valueduring the time period to the suction detection threshold value, andgenerate an alert when the present value exceeds the suction detectionthreshold value on a plurality of consecutive instances during the timeperiod, the alert corresponding to a suction condition.

In another aspect, the time period is a one to five second hysteresiswindow.

In another aspect, the plurality of data values includes a baselinevalue waveform between a 50th to 75th percentile relative to thehysteresis window.

In another aspect, the baseline value waveform is an adaptive value.

In another aspect, the plurality of data values includes a firstpulsatility percentile value between a 5th to 30th percentile relativeto the hysteresis window and a second pulsatility percentile valuebetween a 70th to 95th percentile value relative to the hysteresiswindow.

In another aspect, the control circuit is configured to calculate apulsatility value waveform corresponding to a difference between thefirst pulsatility percentile value and the second pulsatility percentilevalue.

In another aspect, the control circuit is configured to determine thesuction detection threshold value using a suction detection equation,the suction detection equation including adding the baseline valuewaveform to the pulsatility value waveform, the pulsatility valuewaveform being multiplied by a multiplier.

In another aspect, the multiplier is a constant over a plurality of timeperiods.

In another aspect, the control circuit is configured to classify aseverity of the suction condition.

In one aspect, a method for detecting a suction condition in animplantable blood pump includes calculating a plurality of data valuesusing a hysteresis window. A present value during a time periodfollowing the hysteresis window is calculated, the present valuecorresponding to a pump speed divided by a pump current. A suctiondetection threshold value is determined using the plurality of datavalues. The present value during the time period is compared to thesuction detection threshold value. An alert is generated when thepresent value exceeds the suction detection threshold value on at leastone instance during the time period, the alert corresponding to asuction condition.

In another aspect, the time period is a one to five second hysteresiswindow.

In another aspect, the method further includes determining a baselinevalue waveform between a 50th to 75th percentile relative to thehysteresis window.

In another aspect, the method further includes determining a pulsatilityvalue waveform corresponding to a difference between a first pulsatilitypercentile value and a second pulsatility percentile value relative tothe hysteresis window.

In another aspect, the method further includes executing a suctiondetection equation, the suction detection equation including adding thebaseline value waveform to the pulsatility value waveform, thepulsatility value waveform being multiplied by a multiplier.

In another aspect, the multiplier is a constant over a plurality of timeperiods.

In another aspect, the method further includes classifying a severity ofthe suction condition.

In another aspect, the method further includes instantaneouslydetermining the suction condition at an onset thereof.

In another aspect, the method further includes sending the alert to alocation remote from a location of the blood pump.

In another aspect, the method further includes recording the pluralityof instances when the present value exceeds the suction detectionthreshold value using a present waveform.

In one aspect a method for detecting a suction condition in animplantable blood pump includes calculating a baseline value waveformand a pulsatility value waveform relative to a hysteresis window. Apresent value during a time period following the hysteresis window iscalculated, the present value corresponding to a pump speed divided by apump current. a suction detection threshold value is determined usingthe baseline value waveform and the pulsatility value waveform. An alertis generated when the present value exceeds the suction detectionthreshold value on at least one instance during the time period.

In one aspect, a method of detecting an adverse event in an implantableblood pump includes determining a present value at a select time. Thepresent value at the select time minus one is determined. The determinedpresent value at the select time is compared and the determined presentvalue at the select time minus one is compared to a threshold. At leastone pump parameter is adjusted in response to the determined presentvalue at the select time and the determined present value at the selecttime minus one exceeding the threshold.

The details of one or more aspects of the disclosure are set forth inthe accompanying drawings and the description below. Other features,objects, and advantages of the techniques described in this disclosurewill be apparent from the description and drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present invention, and theattendant advantages and features thereof, will be more readilyunderstood by reference to the following detailed description whenconsidered in conjunction with the accompanying drawings wherein:

FIG. 1 is a schematic view of an exemplary blood pump;

FIG. 2 is an exemplary system which may be used to perform one more ofthe method steps of detecting a suction condition within the blood pumpof FIG. 1;

FIG. 3 is a flow chart depicting one more of the method steps ofdetecting the suction condition within the blood pump of FIG. 1;

FIG. 4 is a graph depicting a suction condition shown using a baselinevalue waveform, a present value waveform, and a threshold value waveformover time in accordance with the method of FIG. 3;

FIG. 5 is a graph depicting the suction condition of FIG. 4 shown usinga flow waveform over time;

FIG. 6 is a graph depicting another instance of a suction conditionshown using a flow waveform over time and a present value waveform overtime;

FIG. 7 is a graph depicting another instance of a suction conditionshown using a flow waveform over time, a pump speed waveform over time,and a current waveform over time;

FIG. 8 is a graph depicting a present value waveform relative to timeand three corresponding histograms;

FIG. 9 is a first graph and a second graph depicting a severityclassification of a suction condition; and

FIG. 10 is a graph depicting a change in a present value waveformrelative to time.

DETAILED DESCRIPTION

Before describing in detail exemplary embodiments, it is noted that theconfigurations reside primarily in combinations of system components andmethod steps related to detecting a suction condition within animplantable blood pump. Accordingly, the system and method componentshave been represented where appropriate by conventional symbols in thedrawings, showing only those specific details that are pertinent tounderstanding the configurations of the present disclosure so as not toobscure the disclosure with details that will be readily apparent tothose of ordinary skill in the art having the benefit of the descriptionherein.

As used herein, relational terms, such as “first” and “second,” “top”and “bottom,” and the like, may be used solely to distinguish one entityor element from another entity or element without necessarily requiringor implying any physical or logical relationship or order between suchentities or elements. The terminology used herein is for the purpose ofdescribing particular embodiments only and is not intended to belimiting of the concepts described herein. As used herein, the singularforms “a”, “an” and “the” are intended to include the plural forms aswell, unless the context clearly indicates otherwise. It will be furtherunderstood that the terms “comprises,” “comprising,” “includes” and/or“including” when used herein, specify the presence of stated features,integers, steps, operations, elements, and/or components, but do notpreclude the presence or addition of one or more other features,integers, steps, operations, elements, components, and/or groupsthereof.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this disclosure belongs. It willbe further understood that terms used herein should be interpreted ashaving a meaning that is consistent with their meaning in the context ofthis specification and the relevant art and will not be interpreted inan idealized or overly formal sense unless expressly so defined herein.

In embodiments described herein, the joining term, “in communicationwith” and the like, may be used to indicate electrical or datacommunication, which may be accomplished by physical contact, induction,electromagnetic radiation, radio signaling, infrared signaling oroptical signaling, for example. One having ordinary skill in the artwill appreciate that multiple components may interoperate andmodifications and variations are possible of achieving the electricaland data communication.

Referring now to the drawings in which like reference designators referto like elements there is shown in FIG. 1 an exemplary implantable bloodpump 10 configured to be implanted within a patient, such as a human oranimal patient. The blood pump 10 may be, without limitation, the HVAD®Pump or the MVAD® Pump, having a movable element, such as a rotor,configured to pump blood from the heart to the rest of the body. TheHVAD® Pump is further discussed in commonly owned U.S. Patent Nos.7,997,854 and 8,512,013, and the MVAD® Pump is further discussed incommonly owned U.S. Pat. Nos. 8,007,254, 8,419,609, and 9,561,313, thedisclosures of which are incorporated herein by reference in theentirety.

With reference to FIG. 2, an exemplary system is depicted including theblood pump 10 in communication with a controller 12 and a controlcircuit 14 for monitoring and controlling startup and subsequentoperation of a motor 16 implanted within the blood pump 10 andperforming one or more of the method steps disclosed herein. The methodand system disclosed herein may be used with axial or centrifugal bloodpumps.

In one configuration, the controller 12 and the control circuit 14 areconfigured to detect an adverse event associated with the blood pump 10,such as a suction condition present within the blood pump 10. In orderto detect the suction condition, for example, the controller 12 may beconfigured to determine, monitor, and/or track one or more parametersassociated with the blood pump 10, for example, the amount of powerusage, electrical current, voltage, and/or back electromotive force(“BEMF”), as discussed in commonly owned U.S. Pat. No. 9,511,179, whichis incorporated by reference herein in the entirety. As commonlyunderstood by a person of ordinary skill in the art, BEMF is the voltagein a coil of the motor 16 that opposes current flowing through the coilwhen the armature rotates.

The controller 12 may also include a processor 18 in communication withthe control circuit 14, a memory 20, and an interface 22. The memory 20may be configured to store information accessible by the processor 18,including instructions executable by the processor 18 and/or data thatmay be retrieved, manipulated or stored by the processor 18. Furtherdetails associated with an exemplary controller 12 are disclosed incommonly owned U.S. patent application Ser. No. 15/710,323, which isincorporated by reference herein in the entirety.

FIG. 3 depicts a flowchart of a method 24, i.e., process, for detectingthe suction condition within the blood pump 10 using one or morealgorithms configured to provide an instantaneous detection of thesuction condition, for example, at an onset of the condition or withinone to two seconds of the onset. The method may include calculating oneor more data values, such as a baseline value waveform and a pulsatilityvalue waveform, relative to a hysteresis window and using the datavalues to calculate a suction detection threshold value. A present valuemay be calculated by dividing the pump speed by the pump current,independent of the flow within the blood pump, at a time that followsthe hysteresis window. The suction condition is detected where thepresent value exceeds the suction detection threshold value on at leastone instance.

The method 24 begins at task 26 in which the control circuit 14calculates one or more of the data values based on the hysteresiswindow. Generally speaking, the hysteresis window or hysteresisrepresents a property of a system in which an output value incorporatesa lag, delay, or history dependence, as opposed to being a strictfunction of a corresponding input, as is commonly understood by a personof ordinary skill in the art. The data values may be anticipatedpercentile values and/or a percentage of a minimum, a maximum, or a meanvalue from the hysteresis window calculated when the blood pump 10 isoperating within a normal condition and not a suction condition. Thenormal condition generally includes a daily operating condition typicalfor the individual patient and blood pump 10 when no adverse conditions,such as the suction condition, are present within the blood pump 10.

With reference to FIG. 4, in one configuration, the control circuit 14calculates the baseline value waveform “BV” that is within a 50th to75th percentile of the hysteresis window and the pulsatility valuewaveform “PV” corresponding to a difference between an 70th to 90thpercentile value and a 5th to 30th percentile value relative to thehysteresis window. FIG. 4 is provided for exemplary purposes as the timeperiod, relative percentiles, and values described herein are utilizedfor illustrative purposes and may vary according to criteria input by aclinician or healthcare provider or the algorithms associated with themethod.

At task 28, the control circuit 14 calculates the present valuecorresponding to the pump speed divided by the pump current during atime period, such as a select point or window of time, that may followthe hysteresis window. In other words, the present value is a time-basedsignal in the form of a single number, a range, and/or a waveform. Theterm present value and present value waveform may be usedinterchangeably herein. The pump speed and the pump current may bedetermined using various methods known in the art, such as and withoutlimitation, a speed determination module and a current determinationmodule, as discussed in commonly owned U.S. Pat. No. 9,511,179,referenced above and incorporated herein. With reference to FIG. 4, thepresent value is depicted using a present value waveform, generallydesignated as “PVW,” plotted as rotations per minute (“RPM”) overmilliampere (“mA”) relative to the time period, generally designated as“TP”.

At task 30, the data values, i.e., the anticipated percentile valuesand/or percentages of the minimum, maximum, or mean values from thehysteresis window, are used within a suction detection equation todetermine the suction detection threshold value “TV.” In other words, asuction threshold is calculated using the data values. Referring to FIG.4, the suction detection threshold value TV is shown in dashed dottedlines as a threshold value waveform “TVW” that may be compared to thepresent value to detect the suction condition during the time period“T”. For example, the suction detection equation may include adding thebaseline value waveform to the pulsatility value waveform with thepulsatility value waveform being multiplied by a multiplier “M.” Theequation may appear as: TV at T=BV+PV*M. In one configuration, themultiplier is between 0.5 to 2.0, such as 1.1; however, the multipliermay vary and may be a constant for numerous time periods.

At task 32, the control circuit 14 compares the present value to thesuction detection threshold value. For example, FIG. 4 depicts thepresent waveform PW plotted relative to the threshold value waveformTVW. The suction condition is identified as present or detected when thepresent value is greater than the threshold value on at least oneinstance. FIG. 4 depicts two consecutive suction instances, labeled as“SD1” and “SD2,” where the present waveform PVW exceeds the thresholdvalue waveform TVW.

An alert may be generated at task 34 in response to the suctioncondition detection. The alert is not limited to being activated inresponse to the presence of the suction condition, but may be activatedin response to one or more blood pump parameters or patient diagnosticmetrics exceeding a designated threshold. The alert may be audible,visual, vibratory, or the like, and may be transmitted from a speaker ofthe blood pump 10 and/or the controller 12 to the patient or theclinician at a location remote from the blood pump 10.

With reference to FIG. 5, a flow waveform “FW” is provided depicting thedecrease in flow, i.e., blood flow, relative to a reference region “R”which occurs during the suction condition on the instances SD1 and SD2when the present waveform PW exceeds the threshold value waveform TVW.FIGS. 6 and 7 depict similar graphs illustrating the decrease in flowand the corresponding increase in the present value which may be used todetect the suction condition. In particular, FIG. 6 depicts sixconsecutive decreases in the flow waveform FW occurring simultaneouslywith six consecutive increases in the present waveform PW which indicatethe presence of the suction condition. FIG. 7 depicts six consecutivedecreases in the flow waveform FW occurring simultaneously with sixconsecutive fluctuations in a pump speed waveform “PSW” and sixconsecutive decreases in a current waveform “CW” which indicate thepresence of the suction condition.

Referring now to FIG. 8, as discussed above, the baseline value waveformand the pulsatility value waveform may be determined relative to thehysteresis window. For example, FIG. 8 depicts the present valuewaveform PVW including three data sections ending with designations T1,T2, and T3, containing data used to construct three correspondinghistograms, designated as H1, H2, and H3, respectively. In particular,H1 depicts the baseline value waveform as 3.51, i.e., the 70thpercentile of the present value. In addition, H1 depicts the pulsatilityvalue waveform as 0.11, i.e., the 80th percentile minus the 20thpercentile of the present value from one hundred non-suction timesamples recorded. H2 depicts the baseline value waveform as 3.50 and thepulsatility value waveform as 0.10 from eighty-three non-suction timesamples recorded, while H3 depicts the baseline value waveform as 3.51and the pulsatility value waveform as 0.08 from fifty-four non-suctiontime samples recorded.

With reference to FIG. 9, the control circuit 14 may be configured toclassify a severity of the suction condition, such as by analyzing thepump speed relative to the pump current. During normal operation, thecontroller 12 is configured to maintain a relatively constant pumpspeed, taking into account adjustments to the current to accommodatepump speed changes associated with pressure changes and/or cardiaccontraction. In the presence of the suction condition, the pump speedtypically increases relative to the normal operative speed and thecontrol circuit 14 is configured to reduce the current in an effort toreturn the pump speed to the normal operative speed. As such, greaterfluctuations in the pump speed and the pump current may indicate suctionconditions of greater severity. Such fluctuations in the pump speed maybe graphically plotted relative to the pump current as a loop, with theseverity of the suction condition increasing in accordance with anincrease in an area of the loop.

For example, FIG. 9 includes a first graph “G1” depicting the loophaving one or more severity regions, such as a severe region “SR” insolid lines forming a widest region of the loop and a hazardous region“HR” in dashed lines within the severe region. A mildly severe region“MW” is depicted in dotted lines having a width less than a width of thesevere or hazardous region and a normal region “N” is depicted in solidlines having a relatively narrow width within the severe region. Thesame severity regions are shown in a second graph “G2” plotted as afunction of the pump flow over time. The parameters used to classifyeach severity region may be predetermined by the user, such as aclinician, or may be developed by one or more algorithms associated withthe method. The graphs in FIG. 9 are provided for illustrative purposesand are not intended to be limiting as other classifications may be usedto identify the severity of the suction condition.

Referring now to FIG. 10, an adverse event, such as the suctioncondition, may be detected using an alternative method and algorithmdifferent than method 24 described above. The alternative method andalgorithm includes using a difference in the present value at two ormore different points. Such difference may be analogous to taking aslope of two consecutive present value points. For example, in oneconfiguration, at a select time “t” a change in the present value may beexpressed as a change in present value (“CPV”) at time t=present valueat time t−present value at time (t−1). Such equation may also be writtenas CPV=PV(t)−PV (t−1), where PV=speed/current.

FIG. 10 depicts the data provided in FIGS. 4 and 5 and includes aderived waveform called a “change in present value waveform,” designated“CPVW”. The suction condition is indicated when a change in the presentvalue waveform CPVW is greater than a designated constant “C,” which maybe designated as the threshold. In other words, the CPVW exceeding thethreshold indicates that suction is detected. FIG. 10 depicts thedesignated constant as exemplary value 0.5, however, other values may beused to perform the method and algorithm. In response to the suctioncondition being detected, the method may include adjusting at least onepump parameter, such as the speed, current, etc., of the blood pump 10using the controller 12. The adjustments may be made in attempt toresolve the adverse event. In addition to adjusting the blood pump 10,one or more alarms may be activated in response to the detected suctioncondition or other condition, as discussed above.

It should be understood that various aspects disclosed herein may becombined in different combinations than the combinations specificallypresented in the description and accompanying drawings. It should alsobe understood that, depending on the example, certain acts or events ofany of the processes or methods described herein may be performed in adifferent sequence, may be added, merged, or left out altogether (e.g.,all described acts or events may not be necessary to carry out thetechniques). In addition, while certain aspects of this disclosure aredescribed as being performed by a single module or unit for purposes ofclarity, it should be understood that the techniques of this disclosuremay be performed by a combination of units or modules associated with,for example, a medical device.

In one or more examples, the described techniques may be implemented inhardware, software, firmware, or any combination thereof. If implementedin software, the functions may be stored as one or more instructions orcode on a computer-readable medium and executed by a hardware-basedprocessing unit. Computer-readable media may include non-transitorycomputer-readable media, which corresponds to a tangible medium such asdata storage media (e.g., RAM, ROM, EEPROM, flash memory, or any othermedium that can be used to store desired program code in the form ofinstructions or data structures and that can be accessed by a computer).

Instructions may be executed by one or more processors, such as one ormore digital signal processors (DSPs), general purpose microprocessors,application specific integrated circuits (ASICs), field programmablelogic arrays (FPGAs), or other equivalent integrated or discrete logiccircuitry. Accordingly, the term “processor” as used herein may refer toany of the foregoing structure or any other physical structure suitablefor implementation of the described techniques. Also, the techniquescould be fully implemented in one or more circuits or logic elements.

It will be appreciated by persons skilled in the art that the presentinvention is not limited to what has been particularly shown anddescribed herein above. In addition, unless mention was made above tothe contrary, it should be noted that all of the accompanying drawingsare not to scale. A variety of modifications and variations are possiblein light of the above teachings without departing from the scope andspirit of the invention, which is limited only by the following claims.

What is claimed is:
 1. A system for detecting a suction condition in animplantable blood pump, the system comprising: a controller incommunication with the blood pump, the controller including a controlcircuit configured to: calculate a plurality of data values using ahysteresis window; calculate a present value during a time period, thepresent value corresponding to a pump speed divided by a pump currentfollowing the hysteresis window; determine a suction detection thresholdvalue using the plurality of data values; compare the present valueduring the time period to the suction detection threshold value; andgenerate an alert when the present value exceeds the suction detectionthreshold value on a plurality of consecutive instances during the timeperiod, the alert corresponding to a suction condition.
 2. The system ofclaim 1, wherein the time period is a one to five second hysteresiswindow.
 3. The system of claim 1, wherein the plurality of data valuesincludes a baseline value waveform between a 50th to 75th percentilerelative to the hysteresis window.
 4. The system of claim 3, wherein thebaseline value waveform is an adaptive value.
 5. The system of claim 1,wherein the plurality of data values includes a first pulsatilitypercentile value between a 5th to 30th percentile relative to thehysteresis window and a second pulsatility percentile value between a70th to 95th percentile value relative to the hysteresis window.
 6. Thesystem of claim 5, wherein the control circuit is configured tocalculate a pulsatility value waveform corresponding to a differencebetween the first pulsatility percentile value and the secondpulsatility percentile value.
 7. The system of claim 6, wherein thecontrol circuit is configured to determine the suction detectionthreshold value using a suction detection equation, the suctiondetection equation including adding the baseline value waveform to thepulsatility value waveform, the pulsatility value waveform beingmultiplied by a multiplier.
 8. The system of claim 7, wherein themultiplier is a constant over a plurality of time periods.
 9. The systemof claim 1, wherein the control circuit is configured to classify aseverity of the suction condition.
 10. A method for detecting a suctioncondition in an implantable blood pump, the method comprising:calculating a plurality of data values using a hysteresis window;calculating a present value during a time period following thehysteresis window, the present value corresponding to a pump speeddivided by a pump current; determining a suction detection thresholdvalue using the plurality of data values; comparing the present valueduring the time period to the suction detection threshold value; andgenerating an alert when the present value exceeds the suction detectionthreshold value on at least one instance during the time period, thealert corresponding to a suction condition.
 11. The method of claim 10,wherein the time period is a one to five second hysteresis window. 12.The method of claim 10, further comprising determining a baseline valuewaveform between a 50th to 75th percentile relative to the hysteresiswindow.
 13. The method of claim 12, further comprising determining apulsatility value waveform corresponding to a difference between a firstpulsatility percentile value and a second pulsatility percentile valuerelative to the hysteresis window.
 14. The method of claim 13, furthercomprising executing a suction detection equation, the suction detectionequation including adding the baseline value waveform to the pulsatilityvalue waveform, the pulsatility value waveform being multiplied by amultiplier.
 15. The method of claim 14, wherein the multiplier is aconstant over a plurality of time periods.
 16. The method of claim 10,further comprising classifying a severity of the suction condition. 17.The method of claim 10, further comprising instantaneously determiningthe suction condition at an onset thereof.
 18. The method of claim 10,further comprising sending the alert to a location remote from alocation of the blood pump.
 19. The method of claim 10, furthercomprising recording the plurality of instances when the present valueexceeds the suction detection threshold value using a present waveform.20. A method for detecting a suction condition in an implantable bloodpump, the method comprising: calculating a baseline value waveform and apulsatility value waveform relative to a hysteresis window; calculatinga present value during a time period following the hysteresis window,the present value corresponding to a pump speed divided by a pumpcurrent; determining a suction detection threshold value using thebaseline value waveform and the pulsatility value waveform; andgenerating an alert when the present value exceeds the suction detectionthreshold value on at least one instance during the time period.